1. Field of the Invention
This invention relates to an electrophotographic photosensitive member, an electrophotographic photosensitive member manufacturing process, and a process cartridge and an electrophotographic apparatus which have the electrophotographic photosensitive member.
2. Related Background Art
As an electrophotographic photosensitive member, in view of low costs, high productivity and so forth, what is called an organic electrophotographic photosensitive member has become widely used which includes a cylindrical support and provided thereon a photosensitive layer (organic photosensitive layer) using organic materials as photoconductive materials (such as a charge generating material and a charge transporting material. As for the organic electrophotographic photosensitive member, in view of advantages such as high sensitivity and high durability, an electrophotographic photosensitive member is prevalent having the so-called multi-layer type photosensitive layer composed of a charge generation layer containing a charge generating material such as a photoconductive dye or a photoconductive pigment and a charge transport layer containing a charge transporting material such as a photoconductive polymer or a photoconductive low-molecular weight compound which are superposed one on another.
A cylindrical electrophotographic photosensitive member is commonly used including a cylindrical support and provided thereon a photosensitive layer.
The electrophotographic photosensitive member is used in an electrophotographic image forming process comprising a sequence of a charging step, an exposure step, a developing step, a transfer step and a cleaning step.
In the electrophotographic image forming process, the cleaning step for removing powdered paper, transfer residual toner and so forth present on the peripheral surface of the electrophotographic photosensitive member and cleaning the peripheral surface of the electrophotographic photosensitive member, is important in order to obtain sharp images.
As a method for such cleaning, in view of costs, easiness of design, and so forth, a method is prevalent in which a cleaning blade is brought into contact with the peripheral surface of the electrophotographic photosensitive member not to leave a space between the cleaning blade and the electrophotographic photosensitive member so that the powdered paper and transfer residual toner can be scraped off without leakage.
It has been conventionally rare to use very hard materials in an electrophotographic photosensitive member, and hence problems have often come about such that the electrophotographic photosensitive member significantly abrades to cause undesirable faulty images, or has a shortened lifetime.
Another problem has also come about such that charged products formed through a charging step cause charge generating materials, charge transporting materials, binder resins and so forth to deteriorate and lower electrophotographic performance.
However, in recent years, the selection of materials, the optimization of process conditions of electrophotographic apparatus, and so forth have enabled the abrasion or level of wear of the electrophotographic photosensitive member to be reduced, whereby a longer lifetime has been able to be achieved.
In recent years, a technique is proposed in which a layer with a high hardness is provided as a surface layer of the electrophotographic photosensitive member (the layer that is positioned at the outermost surface of the electrophotographic photosensitive member, in other words, the layer that is positioned farthest from its support) so that the abrasion or level of wear of the electrophotographic photosensitive member can be reduced to allow the electrophotographic photosensitive member to have a longer lifetime (see, e.g., Japanese Patent Applications Laid-open No. H05-034944, No. H05-066598 No. H05-088525 and No. H05-224452).
However, it has turned out that when the peripheral surface of the electrophotographic photosensitive member has a elevated hardness to reduce the abrasion or level of wear, the following problems are raised.
The charged products may be deposited on the electrophotographic photosensitive member and/or the peripheral surface of the electrophotographic photosensitive member may deteriorate because of electrification coming from the charging means, causing image deletion.
The friction between the electrophotographic photosensitive member and the cleaning blade for cleaning the toner remaining on the peripheral surface of the electrophotographic photosensitive member may increase to cause scraping or the blade to turn up.
A phenomenon may occur in which the edge of the cleaning blade is chipped off.
The peripheral surface of the electrophotographic photosensitive member can not easily be abraded even where external additives of the toner, paper dust of the transfer sheet, and so forth are deposited on the peripheral surface of the electrophotographic photosensitive member, and hence the melt adhesion of toner may occur around these foreign particles serving as starting points, increasing a probability of causing scratches on the peripheral surface of the electrophotographic photosensitive member because of the pressure contact with the cleaning blade.
In an attempt to solve the above problems, it is proposed that, e.g., the peripheral surface of the electrophotographic photosensitive member is periodically subjected to abrading, or a means is provided inside the electrophotographic apparatus to subject the peripheral surface of the electrophotographic photosensitive member to abrading (see, e.g., Japanese Patent Applications Laid-open No. H05-204282, No. H05-323833 and No. H06-051674).
However, the former is not effective if the surface roughness resulting from the abrading exceeds a certain suitable range, and the abrading tends to cause deterioration in image formation if such surface roughness goes beyond the certain suitable range. Also, even if the surface roughness is within the suitable range, though effective in the initial stage of the paper feed running, the electrophotographic photosensitive member may gradually abrade during the paper feed running, so that the surface shape may change to tend to cause the above problems after all.
In the latter, there is such a problem that the electrophotographic apparatus itself becomes large-sized. Also, even if such a means for abrading the peripheral surface of the electrophotographic photosensitive member is provided inside the electrophotographic apparatus, since the conditions under which the charged products, the external toner additives, the powderd paper and so forth adhere to the peripheral surface of the electrophotographic photosensitive member during the paper feed running are not constant, it is difficult to find conditions which can solve the problems.